Analytical & Bioanalytical Electrochemistry
Volume:6 Issue: 5, Oct 2014

The purpose of present study was to investigate the corrosion inhibition property of 3-(4-(dimethylamino) phenyl)-1-phenylprop-2-en-1-one(a chalcone, INH-1) derived from condensation of acetophenone and 4, 4- dimethylamino benzaldehyde and three heterocyclics derived from this using Hydrazine (INH-2), Urea (INH-3) and Thiourea (INH-4) on mild steel (MS) in 1M HCl by weight loss and electrochemical methods. It was foundthat inhibition efficiency increases with inhibitor concentration and maximum efficiency was obtained at 25 ppm. Among the studied inhibitors, INH-4 shows the best inhibition efficiency of 98.26 %. Variation of impedance parameters (Rct and Cdl) suggests the formation of protective film of inhibitors on MS surface. The adsorption of inhibitors on MS surface was also studied using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) techniques. The potentiodynamic study reveals that all studied compounds are of mixed type. The adsorption of inhibitors on MS surface was found to follow the Langmuir adsorption isotherm. The weight loss experiment was also performed at different temperature to study the effect of temperature on corrosion rate (CR) and evaluated some thermodynamic parameters.

The effect of chloride ions concentration on the semiconducting behaviors of 1050 and 6061 Al alloys in 0.003 M NaOH has been investigated by using potentiodynamic polarization, cyclic potentiodynamic polarization and Mott-Schottky analysis. Potentiodynamic and cyclic potentiodynamic polarization curves indicate that chloride ionsconcentration narrowed passivation region for both Al alloys. Also, these polarization curves revealed that increasing chloride ions concentration leads to decrease the pitting potential of both Al alloys. Mott–Schottky analysis demonstrated that the passive films formed on both Al alloys in 0.003 M NaOH with and without NaCl addition show n-type semiconducting behaviors in nature. For both alloys, the passive films formed in chloride-free solution are most stable, and that formed in chloride-containing solution are unstable. Also, the Mott– Schottky results showed that the donor density evaluated from the Mott–Schottky plots increases with increasing chloride ions concentration.

In this work the copper electrode modified with thiourea was used for electrocatalytic oxidation of hydrazine in 0.1 M NaOH. The Modified electrode showed excellent character for electrocatalytic oxidation of hydrazine with decrease in overpotential and increase in the anodic current. The kinetic parameters such as the electron transfer coefficient (αa) and the catalytic rate constant (Kcat) for the oxidation of hydrazine were determined. The diffusion coefficient (D) of hydrazine in the solution was also calculated by chronoamperometry. The detection limit (3s) was determined as 7.6 μmol L-1.

The construction and electrochemical response characteristics of six Ciprofloxacin-selective electrodes were investigated using precipitation based technique with sodium tetraphenyl borate (TPB), phosphomolybdate (PMA) and phosphotungstate (PTA); respectively upon using polyvinyl chloride (PVC) matrix and dibutyl phthalate (DBP) as a plasticizer. The resultant sensors have different forms, either as membrane electrodes (sensors 1, 3 and 5) or as coated wire electrodes (sensors 2, 4 and 6). Linear responses of CIP within the concentration ranges of 10−6 to 10−2 mol/L for sensors 1, 2 and 5 while for sensors 3 and 4, the linear responses were within the concentration ranges of 10−5 to 10−2 mol/L and for sensor 6 it shows linear responses within the concentration ranges of 10−7 to 10−2 mol/L. Nernstian slopes of 51.7, 50.7, 58.3, 57.7, 44 and 41.8 mV/decade were observed over the pH range of (5–9) for sensors 1, 2, 5 and 6 and over range of (5-7) for sensor 3 and 4 respectively. The selectivity coefficients of the developed sensors indicated excellent selectivity for CIP. The proposed sensors displayed useful analytical characteristics for the determination of CIP in water samples and pharmaceutical preparation.

The electropolymerziation of aniline blue was carried out in NaOH as a supporting electrolyte by cycling the potential on the carbon paste electrode. The poly (aniline blue) film MCPE used for the votammetric determination of paracetamol at pH 7.2 PBS. Its shows excellent high enhancement and electrocatalytic actvity towards paracetamol at modified carbon paste electrode. The various parameters like effect of scan rate, paracetamol concentration, simulations determination of DA and AA in their sample mixture was analysed by voltammetric technique. The proposed method showed excellent stability and reproducibility.

Ion potentiometric sensors are playing an important role in environmental analysis because of their simplicity and rapidity. In this study, a potentiometric liquid membrane sensor for simple and fast quantification of chromium in various samples was made. Nbanzoyl- N′(6-methyl-2-pyridyl) thiourea was selected as a sensing material in the organic phase of the PVC membrane. The wide linear range (10-6-10-1 mol L-1), low detection limit (3.0×10-7 mol L-1), and fast response time (~5 s) are the characterizations of this electrochemical sensor. The effects of some factors such as internal solution, pH, life time and selectivity were investigated. Finally, it was used for direct determination of chromium and as an indicator electrode in potentiometric titration of chromium ion.

A novel chemically modified electrode containing Rh(III)terpyridine complex was achieved on the surface of glass carbon electrode by sol-gel technique. The electrochemical behavior of modified electrode was characterized by cyclic voltammetry in detail. The filmelectrode obtained was very stable and exhibited electrocatalytic response for oxidation of ascorbic acid. Results showed at bare GC electrode, a small oxidation peak current was observed at about 0.42 V and a well-formed sharp catalytic oxidation peak at about -0.08 V was observed at Rh(III)terpyridine complex modified electrode. The transfer coefficient (α) for electrocatalytic oxidation of ascorbic acid and the diffusion coefficient of this substance under the experimental conditions were also investigated.

Optimization of sulphate bath for deposition of a smooth and uniform Zn-Co alloy over mild steel is discussed in the present work. Electrodeposition was done using Thiaminehydrochloride (THC) and citric acid (CA) as additives in combination. The bath followed anomalous codeposition with preferential deposition of Zn over noble Co. The experimental results reveal that a bright Zn-Co alloy having ~1.06 wt. %Co was showing peak performance against corrosion in compliance with other physical properties like reflectance, hardness, thickness and adhesion. The dependency of bath composition, current density, partial current density, pH and temperature on deposit properties like reflectivity, corrosion resistance were discussed. Deposition was carried out under different condition of c.d.’s and molar ratio of [Co+2]/[Zn+2]. No transition c.d.’s at which codeposition behavior changed from anomalous to normal type was observed. Cyclic polarization measurement was performed to study the nature of corrosion taking place in the corrosion cell. An electrochemical behavior of Zn-Co alloy electrodeposition in alkaline solutions was studied using cyclic voltammetry technique. The increase in the corrosion resistance of coatings attributed to the formation of n-type semiconductor film at the interface was confirmed by Mott-Schottky (M-S) plot with straight line having positive slope. The composition of deposits were determined by colorimetric method and confirmed by EDX analysis. Surface morphology of the deposits was examined using scanning electron microscopy (SEM). The phase content was examined by XRD analysis at different current densities. A stable acid sulphate bath has been proposed for bright and uniform deposit of Zn-Co over mild steel and discussed.

A graphite coated ion selective electrode (GCISE) based on Dibenzo-18-Crown-6 (DB18C6) as a neutral carrier in a Poly Vinyl Chloride (PVC) matrix was fabricated for the determination of K+ ions. The GCISE exhibited a Nernstion slope of 55.3 mV per decade for K+ ion over a wide concentration range of 1.0×10-5 to 1.0×10-1M. The lower detection limit is 5.4×10-6M of KCl. This GCISE had a short response time of 10s, and could be used in a pH range of 2.4 to 9.5. Matched potential method (MPM) was used for determination of selectivity coefficient. High selectivity was obtained over 10 various metal ions. The GCISE was reproducible and stable for a period of two weeks. It was successfully applied in determination of potassium in Oral Rehydration Salts (O.R.S) and mineral water.

A ferrocene-derivative compound, 2,7-bis (ferrocenyl ethynyl) fluoren-9-one (2,7- BFE), was synthesized and used to construct a modified-graphene oxide nano-sheets paste electrode. The electro-oxidation of hydrazine at the surface of the modified electrode was studied using electrochemical approaches. Under the optimized conditions, the square wave voltammetric peak current of hydrazine increased linearly with hydrazine concentrations in the range of 2.2×10-7 to 3.0×10−4 M and a detection limit of 9.8×10−8 M was obtained for hydrazine. Finally this modified electrode was used for determination of hydrazine in some water samples.